Budget M42 turbo build

[gearheadE30]

Woo it's been awhile since I've been around here. Unfortunately I have not progressed much with the engine build. Roadbook rally racing dirt bikes has taken priority and time.

Good luck with the engine refurb.

Curious, how would one describe the sound of preignition detonation in an M42?

It sounds like fluttering paper, is the first thing that comes to mind. Fluttering paper when it's mild, quietly crackling an empty bag of chips when it gets really bad. If you have a loud exhaust or the windows/sunroof are open, you're not going to hear it at all, which is probably why I didn't notice it as much as I could have.

In my case, it also didn't show up at lower intake temps on the street. It took higher intake temps running in boost for many minutes at a time to put it over the edge.

Hey, decided to dig through some old forms and hopefully i can find some answers here. Just wondering what you did ecu wise for the m42. currently doing my own turbo build and i am stuck at this point?

Hope I can help! I went with Megasquirt 2 running the Extra firmware. I've got two cars running MS2E now and have been very happy with them.

[tomevansbutcher]

Hey, decided to dig through some old forms and hopefully i can find some answers here. Just wondering what you did ecu wise for the m42. currently doing my own turbo build and i am stuck at this point?

[robrez]

Good luck with the engine refurb.

Curious, how would one describe the sound of preignition detonation in an M42?

[Victell]

The M42's combustion chamber shape is limited by being a 4 valve engine, and the piston crown is also pretty old school compared to modern squish bands. As a result, you get localized preignition at the top and the bottom of the piston crown.

For your new pistons are you going with a different crown design?

[gearheadE30]

I've finally torn the engine down after having very low compression after the IMS DE. For a 300k mile engine that has been rather abused, it looks fantastic inside. Cylinder bores are fine, head is great, and even the rod and main bearings are serviceable. The cause of the failure has been traced back to collapsed pistons, which is kind of an oddball problem.

My ignition map was overly aggressive, as I may have mentioned, and the result was a bit of pregnition. The M42's combustion chamber shape is limited by being a 4 valve engine, and the piston crown is also pretty old school compared to modern squish bands. As a result, you get localized preignition at the top and the bottom of the piston crown. Mine showed quite a bit of evidence of this, particularly on cylinder 1. I think the piston cooling nozzles (i.e. oil squirters) probably saved my life on this one, considering the oil deposits on the underside of the piston crown. There is no coking, but definitely evidence of heat. It's also kind of a circle of death once the deposits start, as they insulate the piston and hinder cooling. I've seen 20C changes in piston crown temperature changes just from a thin layer of oxidation in the engines developed for work.

So ultimately, the pistons got hot. The result is a slightly deformed top ring with definite evidence of wear, and completely stuck mid rings and oil control rings on all four cylinders. This is why it ran okay, but had a lot of blowby - much of the combustion pressure was going straight past the rings. Based on some FEA magic from a friend who does power cylinder development, it looks like excess heat and load can actually cause the ring grooves to collapse, which is what happened here. They're so stuck that I broke one trying to get it out, and I can't get the bit I broke back into the groove because it collapsed so much.

Fortunately, this makes the rebuild pretty straightforward. New pistons, rings, bearings, all the seals, etc. Also updating to an M44 oil pump and timing case slider instead of the early M42 idler gear. Bonus nachos: with the engine torn down, I can tap the block for the oil drain instead of returning oil flow to the pan below oil level and get rid of my sketchy turbo oil drain vent setup.

[gearheadE30]

I will have to grab a pic of the maps when I get home from the holiday. I'm using table switching with the primary (vacuum up to atmospheric) table modeled after an M50. The secondary (boost) table basically just pulls a degree of timing per PSI of boost from there.

When I was at the track, I had noticed some detonation around peak torque and ended up pulling about 4 degrees of timing across the board by the time I thought I had eliminated it. It must have still been pinging some, but I couldn't hear it in the car. With no knock sensing, it's kind of a crapshoot. I had done most of my tuning on the street, but temperatures overall are somewhat lower, and I hadn't retuned when I built the new exhaust manifold. Since I've had it on the track numerous times with the turbo previously, I'm inclined to think that the new manifold for some reason had more back pressure or something, reducing cylinder evacuation efficiency and increasing knock.


I know all of the pics are down....unfortunately, I am one of the many Photobucket fee structure change victims. I'm not paying hundreds of dollars a year just to get my links back, so I at some point I'll have to rehost elsewhere and put some new pics up.

In the meantime, here's a pic of the car at Putnam:

[downforce22]

Thanks for sharing, whats your timing map look like?

All your pictures are down :/

[gearheadE30]

Wow, only been a few years since I posted here last...

Most recent update is that I took the car to Indianapolis Motor Speedway for a track weekend (3 days) with PCA. I managed to blow up a CV joint, lose a few manifold bolts, break the flange off of my new exhaust manifold, crack both front brake rotors fairly catastrophically even with ducting, and burned through more than half a set of PFC08s. I also burned a hole in at least one piston due to detonation, so I'm in the process of pulling the engine out for a rebuild. Rather than a 6 cylinder swap, I intend to keep the M42 and will likely drop the compression and run a bit more boost.

I think I underestimated the power this car was putting out, as with 7.5 psi and a full interior, it wasn't much slower than a well-built caged and stripped S52 E30 with all the usual bolt ons in a straight line. However, I was obviously running too much timing. The plus side is that, with a new custom oil cooler setup (I'll have to add pics here eventually) I'm keeping temps right around 230F. Intake air temps are also staying within 40F of ambient (which is good; I try to stay within 60F as a goal), coolant temps never went over 211F, and the rest of the car did great.

Here's a quick video:

https://www.youtube.com/watch?v=dS9s-NJwHbk&t=2s

Okay, I give up. No issues embedding on other forums, but it's not working here. Here's a link:

https://www.youtube.com/watch?v=dS9s-NJwHbk&t=2s

[downforce22]

bump updates?

[gearheadE30]

Sweet E30 !
How reliable is the car with the boost setup ?

With 7.5 psi, it has been extremely reliable. I've put something like 30k miles on the turbo setup so far, with a lot of autocrosses thrown in. It has also done maybe 400 miles on the track as well, and the only issues I've had have been high oil temperatures and cooking the brakes, the latter of which is no fault of the turbo.

[BECKSTER]

Sweet E30 !
How reliable is the car with the boost setup ?

[gearheadE30]

Did you ever get this thing on the dyno?

No, I never did. At some point I really should, just to see what kind of numbers it's putting down. I also really need to post some updated pics...looks like the last ones I posted still had the sketchy wastegate piping and such.

electronic boost control parts just came in, by the way. :D

[e30polak]

Did you ever get this thing on the dyno?

[gearheadE30]

For anyone else who finds this in the future looking for an oil cooler solution, here is how the IE cap stacks up.

Original M30B35 oil filter is a Mahle OX41D.
OD: 83mm
ID: 27.7mm top and bottom
H: 128.5mm

The IE cap uses Mahle OX154D:
OD:84mm
ID:42mm, top and bottom
H:106mm

The M42 uses Mahle OX91D:
OX91D:
OD: 82mm
ID: 28mm
H: 88mm

Based on the dimensional differences between the M30 stock vs the IE cap, the new M42 filter would need to be in the vicinity of 65mm tall.

the oil filter housing is aluminum, so this opens the door to possibly welding the M30 upper canister section to the M42 lower section, but I don't know what kind of internal differences there are without buying an M30 canister to measure. They don't appear to be available online, either. At that point, it would probably be easier to remote mount the lube filter somewhere else, or otherwise modify the base for oil diversion and takeoff to a cooler.

[gearheadE30]

Yeah, I had Brembo blanks and HP+ pads on there which was fine before the turbo, and before I knew how to drive all that well, but no luck now. That setup got hot enough to boil the powdercoat off my wheels, turn the wheels yellow (they were silver), bend the backing plates on the pads, and cook all the grease right out of the wheel bearings. It was great. My plan at the moment is brake ducts, Brembo blanks, and Hawk DTC70 pads since I'm a fan of their stuff. I'm sure the Performance Friction pads would work as well.

To be honest, I haven't looked into the M30. I'll do some research tomorrow and measure my housing when I get a chance, but I know the filter is different. Since that cap requires a double lip filter, I'm going to have to do some research to see if something like that exists for the M42. I know the M5X engines have a different cap that isn't compatible.

Yeah, this is an ancient thread. Like I said, I figured it had been lost in the interwebz by now, and then I got an email because of my 4 year old thread subscription, haha. I haven't even hardly been on r3v in probably 3 years...



EDIT: based on the part numbers, the M30 and the early metal-canister M42s use the same oil filter housing cap. The filters are, however, quite different with the M30 being much longer. Next step is to see if there is a filter option out there. Since there are currently no off the shelf solutions for the M42, this is definitely looks promising...

EDIT EDIT: I talked to IE and did some research on Mahle's site, among others, and with the varying dimensions of the filters, there isn't a good off the shelf solution. The guys at IE looked awhile ago for a filter, but nothing that short exists. The only solution to allow the use of that cap would be to siamese an M30 and an M42 housing, so that you can put a tall filter on the M42. In any case, the IE cap reduces the filter media volume by enough that I would be concerned about very short service intervals.